如何在Java中获得arraylist中的所有子级递归

import java.util.ArrayList;

public class RecursiveArrayList {

    public static void main(String[] args) {
        ArrayList<Object> arrayList = new ArrayList<>();
        arrayList.add("A");
        arrayList.add("B");
        ArrayList<Object> subList = new ArrayList<>();
        subList.add("C");
        subList.add("D");
        arrayList.add(subList);

        ArrayList<Object> result = getAllSubItems(arrayList);
        System.out.println(result);
    }

    public static ArrayList<Object> getAllSubItems(ArrayList<Object> arrayList) {
        ArrayList<Object> result = new ArrayList<>();
        for (Object item : arrayList) {
            if (item instanceof ArrayList) {
                result.addAll(getAllSubItems((ArrayList<Object>) item));
            } else {
                result.add(item);
            }
        }
        return result;
    }
}